Mercuiser 140 starting trouble

[walkleyc]

1986 Mercuiser 140 4-cyl, that has trouble starting. It acts as if the fourth cylinder doesn't fire until after a few minutes of warming up. The boat shakes moderate amounts during this period. There is also a little black smoke that happens during this time but again goes away once warm. Once it has warmed up it runs like a top. I was wondering if anyone knows what this is or have any suggestions. Thanks a lot.

 

[vipzach]

Re: Mercuiser 140 starting trouble

It sounds like you have a fuel problem. Black smoke would indicate to rich. What would make you think that the #4 cylinder isn't firing. I would really doubt that is starts firing after it is warmed up. I would check and see if the choke is working.

 

[SeattleMatt]

Re: Mercuiser 140 starting trouble

could also check for water seeping into the valve from a leaky manifold, this would foul the plug until it drys out and blows the water out, <br /><br />might want to do a compression check

 

[Bondo]

Re: Mercuiser 140 starting trouble

You've got a Serious Carb. Problem.........<br /><br />A Rebuild Kit,+ Tune-Up might bring it back........<br /><br />I'm Betting that All 4,.. Not just #4, Plugs are Carbon Fouled..............

 

[walkleyc]

Re: Mercuiser 140 starting trouble

Thanks a lot guys. The reason I thought it was number four was that the plug had a little more carbon on it. I will definitely try the carb rebuild kit and a tune up. Thanks!

 

[trog100]

Re: Mercuiser 140 starting trouble

if that was a car engine it would be the exact symptoms of a leaky headgasket.. when cold the plug is wet and dosnt fire.. the engine will have trouble starting on three.. the black smoke could be just rich mixture from the choke.. the juddering is what any four cylinder engine will do when only running on three.. when the engine warms up the the leak stops (things expand) the plug dries out and it all runs okay.. as the engine cools down the leaks starts up (things contract) and lets a small amount of water into the cylinder to repeat the process..<br /><br />its a boat.. so as well as the head gasket it could be manifold leaks.. same thing either way..<br /><br />trog100<br /><br />ps.. to find out for sure which one it is.. pull the plug leads off one at time till u find one that dosnt make a difference..<br /><br /><br />ps 2.. when u find which one is missing.. remove the plug.. let the engine cool down spin it over and small amounts of water will spit out of the plug hole..

 

[Bondo]

Re: Mercuiser 140 starting trouble

Good Idea trog.............<br /><br />While you've got the Plugs out of the motor Anyway,.............<br /><br />Do a Compression,+ Leakdown Tests............